How do you figure they're exposing themselves to liability if that's the express purpose of the reduced version -- less functionality at a lower price? The only thing I can think of that has kind of a similar feel to it was a case involving contact lenses. The maker sold one kind to be used for a long period for one price, and a different model that had to be replaced more often at a lower price. Thing is, they were actually the same lenses. So the people who paid the high price got what they paid for, and the people who paid the low price actually got MORE than they paid for, but weren't told. So IMHO, noone had a complaint, but someone was suing the company and the courts seemed to at least think it had sufficient merit to allow it to move forward.
Hypothetically, I buy a MSFT abbreviated OS to do security work. MSFT sells a camera program I can use for my security. Watch and monitor my warehouse betweeen certain hours, detect motion, sound alarm, stuff like that. MSFT discontinues the application for whatever reason (which is not uncommon). My intent to use this PC remains the same, now because the competition uses functionality that is intentioanlly 'locked out' by the OS I purchased; I am blackmailed into purchasing another OS to upgrade my security system, which will ultimately perform the same function. For example, I add facial recognition to see that my workers are the only ones moving stuff out the front door.
The stance would be that the hardware was capable of running competitive software, but MSFT used their 'monopoly' status to force me to continue to purchase their products, in an anti-competitive nature, for me to perform a set of functionality that 'could have' been unlimited.
Substitute 'Security' for 'Animation', 'Photoshop', Circuit Design, Media Center, Gaming or whatever. In addition to magnifying the service support efforts (as if XP Media Center, XP Pro 32bit, XP Pro 64bit, Vista Home 32 bit, Vista Home 64 bit, Vista Ultimate 32 Bit, Vista Ultimate 64 bit, Vista Pro, as well as every variety of Win7 - 13 versions there alone) they will not have to support sub-sets of their OS's. This is a can of worms no one should have to open.